One form of a known braking system is the use of friction brakes at the wheels of a vehicle. However, in some instances, for example in the case of a large truck attempting to decelerate while going downhill, friction brakes alone may not be enough to provide the required deceleration. In particular, friction brakes may suffer from “brake fade” in which the braking force which the friction brakes are capable of applying decreases as result of repeated or prolonged use, often as a result of heat build up. A known solution to this problem is to provide the vehicle with a retarder, which operates to slow the vehicle through the transmission, and which can be used in addition to, or instead of, friction brakes. Examples of retarders include an engine brake, compression release brake, exhaust brake, hydraulic retarder, and electric retarder (using electromagnetic induction).
It is known to integrate control of the retarder in the brake pedal of a vehicle. It is also known that operation of the brake pedal by a user leads to using the retarder predominantly, with use of the friction brakes occurring only for occasional heavy braking. This minimizes wear on the brakes, and reduces the likelihood of “brake fade” by reducing the instances and application time of the friction brakes.
However, use of a retarder introduces torque into the transmission which can cause wear of the crown wheel and pinion, and wear of the differential.